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KEY POINTS
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Key Points

  • Autosomal recessive polycystic kidney disease (ARPKD) is characterized by bilaterally enlarged echogenic kidneys.

  • Autosomal dominant polycystic kidney disease (ADPKD) is the most common lethal genetic disease inherited as a dominant Mendelian trait.

  • ARPKD is less common in the general population because of its early mortality, with an incidence of 1:40,000 births.

  • ADPKD has an incidence of 1 in 1000 living individuals with near 100% penetrance.

  • The differential diagnosis of PKD includes Bardet–Biedl syndrome, Meckel–Gruber syndrome, Ivemark syndrome, and Jarcho–Levin syndrome.

  • In the absence of associated malformations, bilaterally symmetrically enlarged echogenic kidneys with renal cysts and oligohydramnios are most likely due to either ARPKD or ADPKD.

  • Renal ultrasound examinations of both parents should be obtained to evaluate for ADPKD.

  • Oligohydramnios-induced pulmonary hypoplasia is a leading cause of perinatol mortality in polycystic kidney disease.

  • The clinical course for prenatally presenting ADPKD is generally milder than for ARPKD.

  • Aggressive neonatal management of infants with ARPKD has led to 1-year survival rates of the order of 82% to 85%.

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CONDITION
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Polycystic kidney disease (PKD) is an inherited disorder with diffuse involvement of both kidneys. Aside from the presence of the cysts, there is no evidence of renal dysplasia. Multiple renal cysts frequently coexist with lesions in other viscera, especially the liver (Kaplan et al., 1989a). A renal cyst is defined as an enclosed sac or nephron segment lined by epithelial cells dilated to more than 200 μm. A cystic kidney is a kidney with three or more cysts present. Cystic kidney disease is the illness caused by a cystic kidney (Kaplan et al., 1989a).

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As early as 1902, it was known that the age distribution of cystic renal disease had two peaks: one close to birth and the other between 30 and 60 years of age (Kaplan et al., 1989b). In general, the use of the term polycystic kidney disease is restricted to single-gene disorders: autosomal dominant PKD (traditionally known as adult onset) and recessively inherited PKD (traditionally known as the infantile form). Since the 1970s, physicians have understood that the adult form can also present during infancy. In the recessive form of PKD, generalized dilatation of the collecting tubules exists, whereas in dominant PKD, cysts develop in localized segments of the kidney anywhere along the nephron (Kaplan et al., 1989a).

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The dominantly inherited form of PKD (ADPKD) is a highly penetrant nephropathy with variable clinical expression that presents mainly during adulthood, but the disease can also occur at any other time during life. Autosomal dominant polycystic kidney disease is the most common lethal genetic disease inherited as a dominant Mendelian trait (Wilson et al., 2006). Mutations in the PKD1 on chromosome 16 and PKD2 on chromosome 4 are responsible for 85% and 15%, respectively, of cases of ADPKD (Harris, 1999). In ADPKD, progressive asymptomatic enlargement of both ...

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